I missed that it was multiple times of calls or emails not returned.
Their original offer to replace a snake that was already doing well, and then stopped eating, was more than many would do. After all, there is no way to know how the customer is keeping the snake. BUT - it would have been much better not to have made the offer at all rather than not to follow through. That leaves a sour note for the customer when it would have been understandable to offer only advice and support in the beginning.
I hope you are able to communicate with them and find out whether they plan to make good on their offer.